Characterisation, bioaccessibility and antioxidant activity of polyphenols from pigmented wheat and barley

Pigmented cereals are believed to be a source of bioaccessible polyphenols which enhance health outcomes through their antioxidant properties. This study aimed to characterise polyphenols from Hordeum vulgare (purple barley), Triticum turgidum (purple wheat) and Triticum aestivum (blue wheat) to evaluate their bioaccessibility and antioxidant activity. Methanol extracts of cereals were used as a control to identify individual polyphenols and quantify their relative antioxidant levels using a UHPLC/MS-Online ABTS•+ system. Digestion of the cereal flour was performed using fluids containing electrolytes, digestive enzymes, and pH alterations to mimic upper gastrointestinal digestion. Using benchtop assays such involving Folin-Ciocalteu, FRAP, DPPH and ABTS•+, the bioaccessibility and antioxidant activity of polyphenols in both the gastric and intestinal phases were determined. Between cereals, the bioaccessible phenolic content was similar following intestinal digestion, but the antioxidant activity was significantly different (purple barley > purple wheat > blue wheat; p < 0.01). Among the polyphenols identified, flavan-3-ols and anthocyanins were the least bioaccessible whereas flavones were the most bioaccessible after digestion. This study demonstrated that these pigmented cereal varieties are sources of bioaccessible polyphenols with antioxidant activity, hence, promoting the value of these grains as potential functional food products.